Method of treating a well using a volatile hydrocarbon liquid

ABSTRACT

A method for treating a subterranean formation surrounding a wellbore wherein a viscous aqueous liquid containing an emulsifying agent and suspended propping agent particles is mixed with a volatile hydrocarbon liquid at a pressure higher than the vapor pressure of the volatile hydrocarbon liquid, and thereafter the mixture is injected through the wellbore and into the formation under conditions to open a fracture in the formation.

United States Patent 1191 Kiel Oct. 23, 1973 [54] METHOD OF TREATING AWELL USING A 3,405,762 10/1968 Terwilliger 166/308 VOLATILE HYDROCARBONLIQUID 3,603,400 9/1971 Son, .lr 166/308 3,664,422 5/1972 Bullen 166/308X Inventor: Othar M. Kiel, Homeworth, Ohio 3,710,865 1 1973 Kiel 166/308[73] Assignee: Esso Production Research Company 3,722,595 3/1973 Kiel166/308 Houston, Tex. Primary Examiner-Stephen J. Novosad [22] 1972Attorney-James A. Reilly et a1. [21] Appl. No.: 281,696

[57] ABSTRACT 16652585116222; A method for treating a subterraneanformation sup n. rounding a wenbore wherein a viscous aqueous liquid[58] Field of Search 166/280, 308, 283; 1

252 8 55 R containing an emulslfymg agent and suspended prop- 1n a enta'rtic es 1s mixe wit a v0 an e rocarp'gg pl' 'dh l'lhyd bon liquid at apressure higher than the vapor pressure [56] Reerences Clted of thevolatile hydrocarbon liquid, and thereafter the UNITED STATES PATENTSmixture is injected through the wellbore and into the 2,802,531 8/1957Cardwell et a1 166/308 X formation under conditions to open a fracturein the 3,108,636 10/1963 Peterson 166/308 formation, 3,368,627 2/1968Hurst et a1.... 166/308 X 3,396,107 8/1968 Hill 166/308 X 19 Claims, 3Drawing Figures 24 BLENDER a '6 9 I8 23 "NI? 14 1 22 1 PUMP PUMP1911351111111 E LIQUID I5 I g 2 Z Z 3 2 3%,: 3%,, 35:,

9 9g 9g 3% I I I I miminmzama 6.766966 SHEET 1 BF 2 I PUMP- CHOOHNOBHVOOHGAH B'ILLVIOA PUMP BLENDER III |:1- -z| FIG. I

WATER NONVOLATILE HYDROCARBON LIQUID car/eases PATENIEU 0U 23 I975 SHEET2 BF 2 I l I l 2 SHEAR RATE RECIPROCAL SECONDS llllll FIG. 2

FIG. 3

SHEAR RATE RECIPROCAL SECONDS METHOD OF TREATING A WELL USING A VOLATILEHYDROCARBON LIQUID BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to a well treating method which employs avolatile hydrocarbon liquid and suspended particulate material. In oneaspect, it relates to the fracturing of subterranean formationssurrounding oil wells, gas wells, and similar boreholes.

2. Description of the Prior Art Stimulation of wells by the hydraulicfracturing technique normally involves the injection of a fracturingfluid into a subterranean formation at a rate and pressure sufficient toinitiate and propagate a fracture therein, and the placement of proppingagent particles in the fracture to prevent the formation from closingfollowing the treatment. The propped fracture provides a highlyconductive channel that extends from the wellbore deep into theformation.

A recent development in hydraulic fracturing techniques involves the useof volatile hydrocarbon liquid as the fracturing fluid. This techniquehas been advantageously employed in the stimulation of gas-producingformations. Its main benefit over fracturing techniques which employ anon-volatile liquid is that the volatile liquid, because of its lowviscosity and tendency to vaporize into a highly mobile gas, may bereadily removed from the formation following the fracturing treatment.

A problem associated with this technique, however, has been that ofincorporating the propping agent particles into the volatile liquid.Since the volatile liquid must be maintained under pressure higher thanits vapor pressure, the propping agent particles normally cannot beblended into the fluid using conventional equipment and techniques. Oneapproach to the problem involves the use of a special blender whichprovides a closed system and permits the propping agent particles to beadded under pressure. The pressurized blenders, however, are not readilyavailable and are not always capable of blending the propping agentparticles into the fluid at the desired concentration. Another approachinvolves the use of a viscous non-volatile liquid as a carrier liquidfor the propping agent particles. Propping agent particles are firstsuspended in the nonvolatile carrier liquid forming a slurry which isthen mixed with the volatile hydrocarbon liquid during injectionoperations. This technique, however, is normally restricted torelatively low concentration of the propping agent particles because oftwo factors: (1) the nonvolatile carrier liquid containing the proppingagentparticles normally constitutes a very minor volume proportion ofthe total fluid used; and (2) the commingling of the nonvolatile liquidand volatile liquid produces a fracturing fluid having a viscosityintermediate that of the viscous nonvolatile liquid and the volatileliquid. Thus, while the viscous nonvolatile liquid may be capable ofsuspending substantial amounts of propping agent, the mixed fluids,either because of the relatively small amount of the carrier fluid orbecause of the reduced viscosity, may not be capable of carrying highconcentrations of the propping agent deep into the formation.

SUMMARY OF THE INVENTION The present invention provides an improvedmethod for introducing particulate material into a fluid containingvolatile hydrocarbon liquid. The method can be employed in fracturingoperations and also in other well treating operations wherein it isdesired to transport and deposit a particulate material into or adjacenta producing formation. Its preferred application, how ever, will be inthe fracturing of gas or condensate formations.

The method employs an emulsion wherein the external phase is, a viscousaqueous liquid and the internal phase is a volatile hydrocarbon liquidsuch as propane, butane, pentane, liquefied petroleum gas, gascondensate having a vapor pressure higher than atmospheric pressure, ormixtures of these with nonvolatile hydrocarbons such as kerosene, dieseloil, light gas oil, and other light and middle distillates, as well aslight crude oil and nonvolatile condensate. In one embodiment, themethod involves blending, at atmospheric pressure, particulate materialhaving a particle size between about 8 and about 100 mesh into a viscousaqueous liquid containing an emulsifying agent to form a slurry; mixingthe slurry and volatile hydrocarbon liquid together, at a pressure abovethe vapor pressure of the hydrocarbon liquid, to form an emulsionwherein the viscous aqueous liquid comprises the external phase and thevolatile hydrocarbon liquid comprises the internal phase; and injectingthe emulsion into a well.

The viscous aqueous liquid constitutes between about 20 and about 80volume percent, preferably between 20 and 50 volume percent, of theemulsion. Its apparent viscosity should be between about 10 centipoisesand about 200 centipoises at F and a shear rate of about 511 reciprocalseconds. This viscosity rdhgbehfii'fs the aqueous liquid to suspendrelatively large quantities of particulate material. A water-solublepolymeric thickening agent such as natural or synthetic polymers may beemployed to impart the desired viscosity to the aqueous liquid.

The concentration of the volatile hydrocarbon liquid in the emulsioncomprises not more than volume percent, and preferably between 50 and 80volume percent of the emulsion. The volatile hydrocarbon liquid at highconcentrations combines with the viscous aqueous phase to produce anemulsion having an apparent viscosity substantially higher than that ofthe viscous aqueous liquid. The high viscosity of the emulsion permitsthe propping agent particles to be carried deep into the formation.

Another embodiment of the invention involves blending the viscousaqueous liquid and a nonvolatile hydrocarbon liquid together to form anoil-in-water emulsion. Particulate material is added to the emulsion toform a slurry which is then mixed with a volatile hydrocarbon liquid ata pressure above the vapor pressure of the volatile hydrocarbon liquid.The nonvolatile and volatile hydrocarbon liquids combine to provide theemulsion with between about 50 and 80 volume percent of an internalhydrocarbon phase. This emulsion is then injected into the well.

The nonvolatile liquid is preferably a light hydrocarbon liquid such asdiesel oil, kerosene, light crude oil, and the like. In some treatments,a stabilized gas condensate may be employed as the nonvolatilehydrocarbon liquid.

A particularly advantageous feature of the present invention is that itpermits the introduction of particulate material into a volatile welltreating fluid using conventional blending equipment.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration ofthe preferred embodiment of equipment capable of performing the methodof the present invention.

FIGS. 2 and 3 are plots of viscosity versus shear rate for variousfluids useable in the method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the presentinvention employs an emulsion comprising an external aqueous phase andan internal hydrocarbon phase which includes a volatile hydrocarbonliquid. The aqueous phase will normally be water containing an effectiveamount of a watersoluble polymeric thickening agent to impart sufficientviscosity to the water to enable it to suspend particulate material. Thewater may be fresh water, water from a public water supply, sea water,salt water, or brine. When treating formations containingwater-sensitive clays, salt water or brine is preferred. Suitablepolymeric thickening agents include natural occurring materials such ascellulose derivatives and guar gum, and synthetic polymers such aspolyacrylamide. The concentration of the polymeric thickening agent inthe water should normally be sufficient to impart an apparent viscositythereto of between about centipoises and about 200 centipoises at 70Fand a shear rate of 51 l reciprocal seconds. The concentration of thethickening agent in the aqueous liquid will normally be between about0.1 and 1.0 weight percent.

A surface-active emulsifying agent capable of forming oil-in-wateremulsions will also be included in the water to ensure thatemulsification is complete before the mixed fluids are introduced intothe formation. A wide variety of emulsifying agents capable of formingoil-in-water emulsions are available. These include anionic, cationic,and nonionic emulsifying agents having hydrophile-lipophile balance(I-ILB) values between about 8 and about 18. Suitable anionicemulsifying agents include the alkali, amine, and other carboxylic acidsoaps. Suitable cationic emulsifying agents include amines of quaternaryammonium salts, aliphatic quaternary ammonium compounds, and thereaction product of an aliphatic quaternary ammonium compound with awater-soluble polysaccharide. Nonionic emulsifying agents capable offorming oil-in-water emulsions include polyoxyethylene sorbitanmonolaurate, polyoxyethylene lauryl ether, polyoxyethylene monostearate,polyoxyethylene oxypropylene stearate, polyoxyethylene cetyl ether,polyoxyethylene sorbitan esters of mixed fatty acids and resin acids,polyoxyethylene glycol monopalmitate, and polyoxyethylene sorbitanmonopalmitate. The concentration of the emulsifying agent in the waterwill normally be between about 0.1 weight percent and about 3.0 weightpercent based on the weight of the aqueous phase.

When employing an anionic emulsifying agent which is sensitive todivalent ions, it will be necessary to use fresh water or softened hardwater as the aqueous liquid. For many of the nonionic and cationicemulsifying agents, however, brine, salt water, or sea water may beemployed.

The volatile hydrocarbon may be any hydrocarbon liquid that has a highvapor pressure higher than atmospheric pressure at surface conditions orone that contains volatile constituents. These include propane, butane,pentane, liquefied petroleum gas (LPG), gas condensate, or mixtures ofthese. The term liquefied petroleum gas" refers to any material composedpredominantly of propane, propylene, butane, butylene, and mixtures ofthese. With the exception of gas condensate and pentane, these liquids,because of their high vapor pressures, must be contained in pressurevessels. Gas condensate comprises the condensable hydrocarbon fractionsproduced from a gas or gas condensate well. Gas condensate, although nothighly volatile, frequently contains volatile constituents which tend tovaporize slowly at atmospheric pressure. When employing condensate thatcontains volatile constituents or pentane at high surface temperatures,it is preferred to introduce these fluids into the system underpressure. Condensate that has been stabilized, however, may be employedas the nonvolatile hydrocarbon as, for example, in the manner describedbelow.

The present invention provides a method for adding particulate materialto a volatile hydrocarbon liquid using conventional blending equipment.In one embodiment, the particulate material is first suspended in theviscous aqueous liquid containing an emulsifying agent using blendingequipment open to the atmosphere. The slurry produced by this operationis blended with the volatile hydrocarbon liquid at a pressure higherthan the vapor pressure of the hydrocarbon liquid to form an emulsion.The emulsion containing the suspended particles is then injected intothe well.

Particulate materials may include sand, plastic pellets, walnut shells,glass beads, metal beads, and the like. The particle size of most ofthese materials, particularly those used in fracturing operations, willbe between about 8 and 100 mesh based on the U. S. Sieve Series. Theconcentration of the particles normally will be between about 1 and 6pounds per gallon of the treating fluid.

As mentioned previously, the viscous aqueous liquid and a nonvolatilehydrocarbon may be emulsified prior to introducing the particulatematerial into the system. The concentration of the nonvolatile liquid inthe emulsion will normally be no more than about volume percent.Particulate material is added to the emulsion at atmospheric pressure toform a slurry. This slurry is then mixed with a volatile hydrocarbonliquid at a pressure higher than the vapor pressure of the volatilehydrocarbon liquid by flowing the two liquids together through aconduit. The addition of the volatile hydrocarbon liquid increases theconcentration of the internal hydrocarbon phase, preferably to a levelof between about 50 and 80 volume percent of the emulsion. Thenonvolatile hydrocarbon liquid which can be kerosene, diesel oil,stabilized condensate, crude oil, or similar light hydrocarbon, aids themixing procedure by increasing the viscosity of the liquid used to carrythe particulate material. It also ensures that an emulsion is formedprior to introduction of the volatile hydrocarbon liquid. Tests haveshown that the volatile hydrocarbon liquid can be blended into theemulsion of the aqueous liquid and nonvolatile hydrocarbon to increasethe concentration of the hydrocarbon phase blender l3, volatilehydrocarbon tanks 12, high pressure pumps l4, l5, and 16, and piping forinterconnecting these components. The blender 13 may be conventionalcomprising a suction pump 19, a blender tub 17 open to the atmosphere,and a discharge pump 18. The blender tub 17 normally includes anagitator paddle and jets for dispersing fluid additives introducedthrough tub openings 21. The discharge of pump 16, through high pressureline 20, is connected to the wellhead 25. The tanks 12 containing thevolatile hydrocarbon liquid are connected to separate pumps 14 and 15which, through lines 22 and 23, are connected to high pressure line 20.

The water and oil tanks and 11 may be steel tanks open to theatmosphere. Since the volume of water normally will be between about 20and about 50 volume percent of the emulsion used to treat the formation,one SOD-barrel water tank will be sufficient for most treatments. In theprocedure that employs an emulsion of water and nonvolatile hydrocarbonliquid, two 500- barrel tanks will normally be sufficient.

The volatile hydrocarbon tanks 12 may be provided by the tank trucksused to transport the volatile hydrocarbon liquid to the well site. Ifthe volatile liquid is to be used only with viscous water, the volume ofvolatile hydrocarbon liquid delivered to the well site should normallybe sufficient to constitute a major volume portion of the emulsion fluidused to treat the well. This normally will require several of thepressurized tanks 12 which can be arranged in banked relation asillustrated in FIG. 1 wherein two tanks feed pump 14 and two tanks feedpump 15. If gas condensate is used as the volatile hydrocarbon, it maybe placed in tanks open to the atmosphere. These tanks will be connectedto high pressure pumps 14 and 15. When using gas condensate, it may benecessary to employ transfer pumps at each tank to pressure feed thehigh pressure pumps 14 and 15.

.In treatments that employ viscous water, a nonvolatile hydrocarbonliquid, and a volatile hydrocarbon liquid, the tankage should normallybe sufficient to contain about equal volumes of these liquids. I

Equipment arrangements other than those described above are possible.For example, transfer pumps may be employed to pump the volatilehydrocarbon liquid and commingle it with the viscous water or emulsionat a location between the blender pump 18 and high pressure pumps 14,15, and 16. In such'an arrangement, the mixture of these liquids may befed to all of the fracturing pumps l4, l5, and 16 through suitablepiping. This arrangement is particularly useful when gas condensate isemployed as the volatile hydrocarbon liquid. 7

In performing a hydraulic fracturing treatment, the equipment may bearranged as illustrated in FIG. 1. Water which can be water from apublic water supply or salt water depending upon the type of emulsifyingagents will first be delivered to the well site and transferred to watertank 10. The polymeric water thickening agent and emulsifying agent willthen be introduced into the water using blender 13. The water may becirculated through the blender l3 and returned to tank 10 while thepolymeric thickening agent and emulsifying agent are introduced into thefluid system through openings 21 of the blender tub 17. Other additivessuch as a water softener or salt may also be added to the water usingblender 13. Following the addition of the additives, the water in tank10 will nonnally be permitted to set for a short period of time, usuallyabout 30 minutes, to permit the additives to completely dissolve orhydrolyze.

After the water in tank 10 has been properly treated, and followingpressure testing of the equipment, pumping operations may commence.Water from tank 10 is flowed through theblender l3 and to the suction ofpump 16. Pump 16 pumps the water at fracturing pressure through highpressure line 20. Simultaneously with this operation, the volatilehydrocarbon liquid is pumped by pumps 14 and 15 and blended into thewater flowing through line 20. The water and hydrocarbon liquid combineto form an emulsion which is injected through the wellbore and into theformation. Preferably, the volatile hydrocarbon liquid is introducedinto line 20 at a plurality of locations to increase the concentrationof the hydrocarbon phase in increments. The rates at which the water andvolatile hydrocarbon liquid are pumped and combined are sufficientlyhigh to open a fracture in the formation. The pumping rate will normallybe between about 5 and 30 barrels per minute. Propping agent particlesnormally will not be introduced into the fluid until a fracture ofsufficientdynamic geometry has been created to permit the entry of thepropping agent particles. During this initial operation, however, it maybe desirable to add a fluid loss additive such as silica flour to thefracturing fluid. This may be done by introducing the silica flour intothe blender tub 17 through openings 21. From about 10 to about 60 poundsof the fluid loss additive per 1,000 gallons of the fracturing fluid areused in most treatments. The pumps l4, l5, and 16 are operated toprovide the proper water-to-hydrocarbon liquid volume ratio whichpreferably will be between 1:1 and 1:4. After a fracture of the desireddynamic geometry has been created, the propping agent particles areblended into the viscous water by introducing them through openings 21of blender tub 17. The concentration of the propping agent particles inthe viscous water should be sufficiently high to provide the properconcentration in the total fracturing fluid. In a typical treatmentwherein the volume ratio of water-to-volatile hydrocarbon is 1:2, theconcentration of the propping agent particles in the water should beabout three times that desired for the total fracturing fluid. Thus, ifit is desired to provide the treating fluid with 3 pounds of proppingagent per gallon of the emulsion, the prop- V ping agent particles willbe added to the viscous water in a concentration of about 9 pounds pergallon. The slurry of viscous water and propping agent particles and thevolatile hydrocarbon liquid are flowed together in line 20. The waterand hydrocarbon liquid combine to form an emulsion and the proppingagent particles become dispersed in the emulsion. The emulsion has anapparent viscosity substantially higher than that of the viscous water.The high viscosity of the emulsion permits the propping agent particlesto be carried deep into the fracture. The emulsion containing thepropping agent particles may be followed with an afterflush liquid todisplace it from the wellbore. A volatile hydrocarbon liquid or leasecondensate may be used for this purpose. Following pumping operations,the well is shut in to permit the emulsion to bleed off into theformation causing the fracture to close on the propping agent particles.

When the well is placed on production, the volatile hydrocarbon liquidtends to vaporize at formation conditions, particularly in the vicinityof the wellbore where the pressure has been reduced. The vaporizationmay be aided by formation gas commingling with the volatile hydrocarbonliquid in the fracture or formation matrix. The volatile hydrocarbonliquid also aids in the production operation by reducing the hydrostaticpressure within the wellbore. When the well is placed on production, thefracturing fluid remaining in-the wellbore will vaporize, reducing thefluid column above the producing formation, and thereby induce the wellto flow. This is an important feature when treating low pressuregas-producing formations.

The method embodiment that employs an emulsion of water and anonvolatile hydrocarbon liquid is basically the same as that describedabove except that the viscous water and nonvolatile hydrocarbon areemulsified prior to introducing the propping agent particles.Emulsification of these liquids may be performed by flowing the liquidstogether as at 24 and then flowing this mixture through the blender 13.The mixture may be recirculated to tank 11 until the nonvolatilehydrocarbon is uniformly dispersed in the water. Alternatively, it maybe flowed directly from the blender 13 to the high pressure pump 16.Volatile hydrocarbon liquid is added to the emulsion in line by means ofpump 14 and/or pump 15.

Variations in the treatement described above include using, in lieu ofthe emulsion to initiate and propagate the fracture, a separate fluidsuch as a gelled hydrocarbon for this purpose. This fluid may beinjected into the formation to initiate and generate the fracture andmay be followed with the emulsion containing the propping agentparticles and the volatile hydrocarbon liquid.

From the foregoing, it will be apparent that numerous variations in thefluid formulation, fluid additives, and injection procedures arepossible. A typical treatment, however, may be as follows. Five hundredbarrels of water are placed in tank 10. Four high pressure vesselscontaining a total of about 1,200 barrels of a com wellbore. The well isthen shut in to permit the emulsion to bleed off into the formationwhich causes the fracture to close on the propping agent particles. lfdesired, a spacer fluid consisting of the emulsion free of any suspendedsolids may be used between the emulsion containing the fluid lossadditive and the emulsion containing the propping agent particles.

A series of laboratory tests were conducted to determine the rheologicalproperties of an emulsion containing volatile hydrocarbon liquid.Samples were prepared by the following procedure. An emulsifier and guargum were first added to brine (saturated NaCl solution) to formthicknened water. The emulsifier was a long chain quarternary ammoniumchloride marketed by Enjay Chemical as a cationic emulsifier under thetradename Corexit 8596." The thickened water had an apparent viscosityof about 47 centipoises at 70F and a shear rate of 51 l reciprocalseconds. Using a lucite pressure cell, n-butane or a mixture of n-butaneand No. 2 diessel oil was then emulsified in the thickened water under apressure of about 20 psig. When using a mixture of n-butane and dieseloil as the hydrocarbon phase, the brine and diesel oil were firstemulsitied and the n-butane added to this emulsion under pressure.Emulsification of all samples was rapid requiring only a few shakes ofthe pressure cell to disperse the hydrocarbon liquid in the brine. Eachemulsion sample was cooled to a vapor pressure below atmosphericpressure and transferred to a Fann Model 50 B viscometer which had beenchilled to minimize flashing of the sample. The sample in the viscometerwas pressurized with dry nitrogen and shear stress versus shear ratecurve was recorded at various temperatures. The apparent viscosityversus shear rate curve was then plotted for each measurement.

FIGS.-2 and 3 present apparent viscosity versus shear rate data for thevarious emulsions tested. The emulsions tested, identified as A, B, C,and D on the plots,

had the following compositions.

Emulsion A Emulsion B Emulsion C Emulsion D Aqueous phase:

Brine, vol. percent of emulsion 33 33 25 Emulsifier, wt. percent inbrine 0.42 0.42 0.42 0.42 Guar gum, wt. percent in brine 0.48 0.48 0. 480.48 Hydrocarbon phase:

n-Butane, vol. percent of emulsion- 33 67 50 Diesel oil, vol. percent ofemulsion 34 50 25 mercial LPG are connected to high pressure pumps 14and 15. About 100 gallons of an emulsifying agent and about 1,000 poundsof guar gum are added to and dispersed in the water. The viscous wateris pumped through high pressure line 20 while LPG is blended therein toprovide a water-to-LPG volume ratio of about 1:2. During this initialpumping stage, a fluid loss additive is blended into the viscous waterat a concentration of about pounds per 1,000 gallons. About 750 barrelsof the viscous water and LPG mixture are injected into the well atmaximum permissible rates to initiate and propagate a fracture in theformation. Immediately following this and while continuing pumping atabout the same volumetic rates, a 20-40 mesh sand is blended into theviscous water at a concentration of about 9 pounds per gallon. Duringthis stage, the fluid loss additive is not used. The viscous water andsand slurry mix with the LPG in line 20 and the sand disperses in themixture in a concentration of about 3 pound per gallon. About 750barrels of the viscous water and LPG mixture containing the same areinjected into the well to displace the emulsion from the In regard tothe present invention relating to the addition of particulate materialto an emulsion containing a volatile hydrocarbon liquid, it should be.noted that the apparent viscosity of the final emulsion issubstantially higher than that of the aqueous phase alone. It shouldalso be noted that the addition of n-butane to an emulsion of diesel oiland brine increases the viscosity of the emulsion (compare Emulsion Aand Emulsion B). This increase in viscosity is particularly important infracturng operations because high apparent viscosity permit the proppingagent particles to be transported deep into the fracture.

I claim:

1. A method for treating a well using a fluid containing a volatilehydrocarbon liquid which comprises blending into a viscous aqueousliquid containing an emulsifying agent capable of forming anoil-in-water emulsion, particulate material having a particle sizebetween about 8 and about 100 mesh to form a slurry; mixing said slurryand said volatile hydrocarbon liquid together at a pressure above thevapor pressure of said volatile hydrocarbon liquid to form an emulsionwherein the viscous aqueous liquid comprises the external phase andconstitutes at least 20 volume percent of the emulsion and the volatilehydrocarbon liquid comprises the internal phase and constitutes no morethan about 80 volume percent of the emulsion; and injecting saidemulsion into said well. I

2. A method as defined in claim 1 wherein the particulate material isblended into said viscous aqueous liquid at atmospheric pressure.

3. A method as defined in claim 1 wherein the amount of particulatematerial blended into said viscous aqueous liquid is sufficient toprovide a concentration of betweenabout l and 6 pounds of saidparticulate material per gallon of said emulsion.

4. A method as defined in claim 1 wherein said volatile hydrocarbonliquid is propane.

5. A method as defined in claim 1 wherein said volatile hydrocarbonliquid is butane.

6. A method as defined in claim 1 wherein said volatile hydrocarbonliquid is liquid petroleum gas.

7. A method as defined in claim 1 wherein said viscous aqueous liquidhas an apparent viscosity between about and about 200 centipoises at 70Fand a shear rate of about 511 reciprocal seconds.

8. A method as defined in claim 7 wherein said viscous aqueous liquidcomprises water. containing a water-soluble polymeric thickening agent.

9. A method as defined in claim 8 wherein the polymeric thickening agentis polyacrylamide.

10. A method as defined in claim 8 wherein the polymeric thickeningagent is guar gum.

11. A method as defined in claim 1 wherein the concentration of thevolatile hydrocarbon liquid in the emulsion is between about 50 volumepercent and about 80 volume percent.

12. A method of treating a well which comprises blending together anonvolatile hydrocarbon liquid and a viscous aqueous liquid containingan emulsifying agent to form an emulsion wherein the viscous squeousliquid comprises the external phase and the nonvolatile hydrocarbonliquid comprises the internal phase; blending intosaid emulsionparticulate material having a particle size between about 8 and about100 mesh to form a slurry; mixing said slurry and a volatile hydrocarbonliquid together at a pressure above the vapor pressure of said volatilehydrocarbon liquid to increase the concentration of said hydrocarbonphase of said emulsion to between about 50 and about 80 volume percent;and thereafter injecting said emulsion containing said volatilehydrocarbon and said particulate mate-' rial into said well. v

13. A method as defined in claim 12 wherein said nonvolatile hydrocarbonliquid comprises not more than about 50 volume percent of the emulsionof said viscous aqueous liquid and said nonvolatile hydrocarbon liquid.

14. A method as defined in claim 12 wherein said volatile hydrocarbonliquid comprises at least 50 volume percent of said hydrocarbon phase.

15. A method as defined in claim 12 wherein said nonvolatile hydrocarbonliquid is a gas condenste.

16. A method for the hydraulic fracturing of a subterranean formationsurrounding a wellbore using a volatile hydrocarbon liquid whichcomprises blending into a viscous aqueous liquid containing anemulsifying agent capable of forming an oil-in-water emulsion, proppingagent particles having a particle size between about 8 and about 100mesh to form a slurry; flowing said slurry at a pressure above the vaporpressure of said hydrocarbon liquid through a conduit; commingling saidvolatile hydrocarbon'liquid with said slurry in said conduit to form anemulsion wherein the viscous aqueous liquid comprises the external phaseand constitutes at least 20 volume percent of the emulsion and thevolatile hydrocarbon liquid comprises the internal phase and constitutesno more than 80 volume percent of the emulsion; and injecting saidemulsion into said wellbore at a pressure sufficient to open a fracturein saidformation.

l7. Amethod for the hydraulic fracturing of a subterranean formationsurrounding a wellbore using a volatile hydrocarbon liquid whichcomprises forming an emulsion which includes a viscous aqueous liquid asthe external phase and a nonvolatile hydrocarbon as the internal phase;suspending in said emulsion propping agent particles having a particlesize between about 8 and 100 mesh, flowing said emulsion containing thesuspended propping agent particles through a conduit at a pressure abovethe vapor pressure of said volatile hydrocarbon liquid; introducing intosaid conduit said volatile hydrocarbon liquid to increase theconcentration of said hydrocarbon phase of said emulsion to betweenabout 50 and about 80 volume percent, and thereafter injecting saidemulsion containing said volatile hydrocarbon liquid and said suspendedpropping agent particles into said formation at a pressure sufficient toopen a fracture in said formation.

18. A method for the hydraulic fracturing of a subterranean formationsurrounding a wellbore using a volatile hydrocarbon liquid whichcomprises blending into a viscous aqueous liquid containing anemulsifying agent capable of forming an oil-in-water emulsion proppingagent particles to form a slurry, pumping said slurry through a conduitand into said wellbore at a pressure above the vapor pressure of saidvolatile hydrocarbon liquid, said pressure bieng sufficient to open afracture in said formation; and commingling with said slurry flowingthrough said conduit said volatile hydrocarbon liquid to form anemulsion wherein the viscous aqueous liquid comprises the external phaseand constitutes at least 20 volume percent of the emulsion and saidvolatile hydrocarbon liquid comprises the internal phase and constitutesno more than 80 volume percent of the emulsion.

19. A method for the hydraulic fracturing of a subterranean formationsurrounding a wellbore using a volatile hydrocarbon liquid whichcomprises forming an emulsion which includes a viscous aqueous liquid asthe external phase and a nonvolatile hydrocarbon liquid as the internalhydrocarbon phase; blending propping agent particles into said emulsionto form a slurry;

pumping said slurry through a conduit and into said ing said volatilehydrocarbon liquid into said conduit to mix with said emulsion andthereby increase the concentration of said internal hydrocarbon phase ofsaid emulsion to between about 50 and about volume percent.

i i i

2. A method as defined in claim 1 wherein the particulate material isblended into said viscous aqueous liquid at atmospheric pressure.
 3. Amethod as defined in claim 1 wherein the amount of particulate materialblended into said viscous aqueous liquid is sufficient to provide aconcentration of between about 1 and about 6 pounds of said particulatematerial per gallon of said emulsion.
 4. A method as defined in claim 1wherein said volatile hydrocarbon liquid is propane.
 5. A method asdefined in claim 1 wherein said volatile hydrocarbon liquid is butane.6. A method as defined in claim 1 wherein said volatile hydrocarbonliquid is liquid petroleum gas.
 7. A method as defined in claim 1wherein said viscous aqueous liquid has an apparent viscosity betweenabout 10 and about 200 centipoises at 70*F and a shear rate of about 511reciprocal seconds.
 8. A method as defined in claim 7 wherein saidviscous aqueous liquid comprises water containing a water-solublepolymeric thickening agent.
 9. A method as defined in claim 8 whereinthe polymeric thickening agent is polyacrylamide.
 10. A method asdefined in claim 8 wherein the polymeric thickening agent is guar gum.11. A method as defined in claim 1 wherein the concentration of thevolatile hydrocarbon liquid in the emulsion is between about 50 volumepercent and about 80 volume percent.
 12. A method of treating a wellwhich comprises blending together a nonvolatile hydrocarbon liquid and aviscous aqueous liquid containing an emulsifying agent to form anemulsion wherein the viscous aqueous liquid comprises the external phaseand the nonvolatile hydrocarbon liquid comprises the internal phase;blending into said emulsion particulate material having a particle sizebetween about 8 and about 100 mesh to form a slurry; mixing said slurryand a volatile hydrocarbon liquid together at a pressure above the vaporpressure of said volatile hydrocarbon liquid to increase theconcentration of said hydrocarbon phase of said emulsion to betweenabout 50 and about 80 volume percent; and thereafter injecting saidemulsion containing said volatile hydrocarbon and said particulatematerial into said well.
 13. A method as defined in claim 12 whereinsaid nonvolatile hydrocarbon liquid comprises not more than about 50volume percent of the emulsion of said viscous aqueous liquid and saidnonvolatile hydrocarbon liquid.
 14. A method as defined in claim 12wherein said volatile hydrocarbon liquid comprises at least 50 volumepercent of said hydrocarbon phase.
 15. A method as defined in claim 12wherein said nonvolatile hydrocarbon liquid is a gas condensate.
 16. Amethod for the hydraulic fracturing of a subterranean formationsurrounding a wellbore using a volatile hydrocarbon liquid whichcomprIses blending into a viscous aqueous liquid containing anemulsifying agent capable of forming an oil-in-water emulsion, proppingagent particles having a particle size between about 8 and about 100mesh to form a slurry; flowing said slurry at a pressure above the vaporpressure of said hydrocarbon liquid through a conduit; commingling saidvolatile hydrocarbon liquid with said slurry in said conduit to form anemulsion wherein the viscous aqueous liquid comprises the external phaseand constitutes at least 20 volume percent of the emulsion and thevolatile hydrocarbon liquid comprises the internal phase and constitutesno more than 80 volume percent of the emulsion; and injecting saidemulsion into said wellbore at a pressure sufficient to open a fracturein said formation.
 17. A method for the hydraulic fracturing of asubterranean formation surrounding a wellbore using a volatilehydrocarbon liquid which comprises forming an emulsion which includes aviscous aqueous liquid as the external phase and a nonvolatilehydrocarbon as the internal phase; suspending in said emulsion proppingagent particles having a particle size between about 8 and 100 mesh,flowing said emulsion containing the suspended propping agent particlesthrough a conduit at a pressure above the vapor pressure of saidvolatile hydrocarbon liquid; introducing into said conduit said volatilehydrocarbon liquid to increase the concentration of said hydrocarbonphase of said emulsion to between about 50 and about 80 volume percent,and thereafter injecting said emulsion containing said volatilehydrocarbon liquid and said suspended propping agent particles into saidformation at a pressure sufficient to open a fracture in said formation.18. A method for the hydraulic fracturing of a subterranean formationsurrounding a wellbore using a volatile hydrocarbon liquid whichcomprises blending into a viscous aqueous liquid containing anemulsifying agent capable of forming an oil-in-water emulsion proppingagent particles to form a slurry, pumping said slurry through a conduitand into said wellbore at a pressure above the vapor pressure of saidvolatile hydrocarbon liquid, said pressure being sufficient to open afracture in said formation; and commingling with said slurry flowingthrough said conduit said volatile hydrocarbon liquid to form anemulsion wherein the viscous aqueous liquid comprises the external phaseand constitutes at least 20 volume percent of the emulsion and saidvolatile hydrocarbon liquid comprises the internal phase and constitutesno more than 80 volume percent of the emulsion.
 19. A method for thehydraulic fracturing of a subterranean formation surrounding a wellboreusing a volatile hydrocarbon liquid which comprises forming an emulsionwhich includes a viscous aqueous liquid as the external phase and anonvolatile hydrocarbon liquid as the internal hydrocarbon phase;blending propping agent particles into said emulsion to form a slurry;pumping said slurry through a conduit and into said wellbore at apressure sufficient to open a fracture in said formation, said pressurebeing above the vapor pressure of said volatile hydrocarbon liquid;introducing said volatile hydrocarbon liquid into said conduit to mixwith said emulsion and thereby increase the concentration of saidinternal hydrocarbon phase of said emulsion to between about 50 andabout 80 volume percent.